Using a make-shift sound-card oscilloscope, I would like to do AC sweeps of circuits designed for direct electric guitar output (preamps). However I'm having trouble creating an equivalent circuit that takes the relatively low impedance sound card output and converts it to high impedance to roughly emulate an e-guitar.

I tried just sticking a big resistor in series but that cuts the voltage and the PC output voltage cannot be increased enough to compensate.

My understanding is that the output of an electric guitar is around 1V with 250K impedance and thus outputs minute amounts of current. The sound card is about 1V with 50Ohms impedance and thus can output much greater amounts of current.

So I reconnoiter I need a specialty signal-transformer. Is there an audio transformer that has a 50Ohm primary and 200K secondary? Or since I suspect the voltage will be increased it could be less and then I could also add a resistor in series so that the result is 1V with 200K

Also does anyone have any thoughts about trying to match the unique frequency response of an e-guitar. If not, that's ok. For now I will settle for a flat response.

Also, I would be interested in hearing about exactly how I might use an external coil to drive pickups directly on an actual guitar. Meaning, take the sound card output and send it to a coil of magnet wire resting on top of a pickup.

Any ideas?

Mike

Twaksak

10th August 2009 10:22 AM

Impedace

Hi Mike

I have made a couple of electric guitar amps for my sons band with just guitar preamp with tone controls coupled to a poweramp. He uses electric guitars with passive pots, acoustic guitars with active tone controls and sometimes a distortion pedal before the amplifier input. They all seem to work with a preamp designed for normal guitar.

Hope this helps
Chris

Artie

12th May 2010 10:00 PM

Go here, and scroll down to where you see "Guitar Pickup Simulation". That should help.